The invention relates to a device for acquiring information contained in a phosphor layer.
X-ray pictures, in particular for medical purposes, are recorded using phosphor layers, whereby the x-radiation that passes through an object, for example a patient, is stored as a latent image in the phosphor layer. To read the latent image, the phosphor layer is irradiated with excitation light, causing it to emit emission light corresponding to the latent image; said emission light being acquired by an optical detector and converted into electrical signals. The electrical signals may be processed as needed and displayed on a monitor or output using a respective output device such as a printer, for example.
Such a device is the subject of the German Patent No. DE 198 59 747 C1, whereby reflection layers for reflecting the excitation light are provided between the phosphor layer and the detector. In addition to the reflection layers, an absorption filter for absorbing the excitation light can be inserted in the beam path between the phosphor layer and the detector. Reflecting or absorbing the excitation light prevents this excitation light from reaching the detector, and in doing so from falsifying the measurement of the emission light emitted by the phosphor layer.
With these known filter devices, high contrasts, i.e., differences in the transparency of the filter device for emission light in relation to the excitation light, can be achieved. High contrasts are required for the described applications because the emission light that is excited in the phosphor layer has, as a rule, an intensity that is several orders of magnitude smaller than the excitation light, and if the contrasts were not sufficiently great, the measurement of the emission light would be falsified. Thus, for certain applications, for example, when using certain detector types or certain types of phosphor layers, it may be desirable to achieve even greater contrasts in order to ensure greater reliability when measuring the emission light.